1. Field of the Invention
The present invention relates to a barium borosilicate glass and a glass ceramic composition useful for insulating pastes for electronic parts, ceramic color pastes for automobile windows, glazes for dishes and the like.
2. Discussion of Background
A glass powder or a glass ceramic composition containing a glass powder is widely used for e.g. insulating pastes for electronic parts and ceramic color pastes for automobile windows. Hereinafter, the glass powder and the glass ceramic composition will be referred to as a glass frit.
A glass frit for the above applications is required to have various properties, and various glass frits are used depending upon the properties required. For example, a glass frit containing lead, bismuth or cadmium has been conventionally used as a glass frit having excellent water resistance and acid resistance and capable of being fired at a temperature of from 600 to 850xc2x0 C.
In recent years, as a glass frit having such properties, one containing no lead, bismuth nor cadmium has been required.
It is an object of the present invention to provide a glass and a glass ceramic composition containing no lead, bismuth nor cadmium, and having a softening point and a thermal expansion coefficient suitable for various applications, particularly for an application wherein a chemical durability such as water resistance is required and the firing temperature is from 600 to 850xc2x0 C.
The present invention provides a barium borosilicate glass which consists essentially of, as represented by wt %:
and a glass ceramic composition which comprises, as represented by mass%, from 50 to 99.9% of a powder of said barium borosilicate glass, from 0 to 50% of a ceramic filler and from 0 to 30% of a heat resistant pigment, wherein the total content of the ceramic filler and the heat resistant pigment is from 0.1 to 50%.
The barium borosilicate glass of the present invention (hereinafter referred to simply as the glass of the present invention) is usually formed into a powder, followed by coating and firing to obtain a sintered product, and used as a powder.
The powder of the glass of the present invention may be kneaded with a vehicle containing a resin component such as ethyl cellulose and a solvent such as xcex1-terpineol to obtain a paste, which is used for e.g. screen printing. Otherwise, it may be formed into a slurry, which is then formed into a green sheet, and a multi-layer construction may be prepared by using said green sheet. Here, the multi-layer construction may, for example, be prepared in such a manner that e.g. an electronic circuit pattern is formed on the green sheet by e.g. screen printing, and the resulting green sheets are laminated, followed by firing.
The powder of the glass of the present invention is useful for e.g. insulating pastes for electronic parts, materials for sealing electronic parts, color pastes for automobile windows and glazes for dishes. Examples of the insulating pastes for electronic parts include overcoat pastes for hybrid IC (HIC), crossover pastes for HIC, multi-layer insulating glass pastes for HIC and overcoat pastes for print heads.
The glass of the present invention has a softening point (TS) i.e. a softening point by a differential thermal analysis of preferably from 600 to 800xc2x0 C. If it is less than 600xc2x0 C., softening flow tends to be too significant during firing at a temperature of from 600 to 850xc2x0 C., even if e.g. a ceramic filler is used together. It is more preferably at least 630xc2x0 C., particularly preferably at least 650xc2x0 C. If it exceeds 800xc2x0 C., softening flow tends to be too small during firing at a temperature of from 600 to 850xc2x0 C. It is more preferably at most 770xc2x0 C., particularly preferably at most 750xc2x0 C.
It is preferred that the glass of the present invention is less likely to undergo crystallization during firing. Namely, the glass of the present invention has a crystallization temperature (TC) of preferably at least 950xc2x0 C., or a difference between TC and TS (TC-TS) of preferably at least 50xc2x0 C. (TC-TS) is more preferably at least 100xc2x0 C., particularly preferably at least 130xc2x0 C. Here, TC is a crystallization peak temperature obtained by a differential thermal analysis, and in a case where no crystallization peak is confirmed even if the differential thermal analysis is carried out up to 1,000xc2x0 C., TC is assumed to be infinite (∞).
The average coefficient of linear expansion of the glass of the present invention at a temperature of from 50 to 350xc2x0 C., i.e. the above average coefficient of linear expansion of the sintered product of the powder of the glass of the present invention, is preferably from 55xc3x9710xe2x88x927 to 100xc3x9710xe2x88x927/xc2x0 C. If it is less than 55xc3x9710xe2x88x927/xc2x0 C., expansion coefficient matching with e.g. an AlN substrate having the above average coefficient of linear expansion of, for example, 45xc3x9710xe2x88x927/xc2x0 C., tends to be difficult, whereby application in which coating on e.g. an AlN substrate and firing are carried out, tends to be difficult. If it exceeds 100xc3x9710xe2x88x927/xc2x0 C., expansion coefficient matching with e.g. soda lime silica glass having the above average coefficient of linear expansion of, for example, 78xc3x9710xe2x88x927/xc2x0 C., tends to be difficult, even if e.g. a filler is used together, whereby application in which coating on e.g. a soda lime silica glass and firing are carried out, tends to be difficult. It is more preferably at most 85xc3x9710xe2x88x927/xc2x0 C. Hereafter the average coefficient of linear expansion at a temperature of from 50 to 350xc2x0 C. will be referred to simply as expansion coefficient.
The glass of the present invention preferably consists essentially of, as represented by mass% based on the following oxides:
Now, the composition of the glass of the present invention will be described below, representing by mass%.
B2O3 is a network former and essential. If it is less than 5%, the softening point tends to be too high. It is preferably at least 7%, more preferably at least 8%. If it exceeds 35%, the chemical durability, particularly water resistance, will decrease. It is preferably at most 33%.
SiO2 is a network former and essential. If it is less than 0.5%, the chemical durability, particularly water resistance, will decrease. It is preferably at least 0.7%, more preferably at least 5%, particularly preferably at least 6%. If it exceeds 30%, the softening point tends to be too high. It is preferably at most 28%, more preferably at most 26%.
The total of contents of B2O3 and SiO2 is preferably at most 49%, more preferably at most 47%.
BaO is a flux component and essential. If it is less than 25%, the softening point tends to be too high. It is preferably at least 27%, more preferably at least 28%. If it exceeds 75%, the glass tends to be devitrified during melting. It is preferably at most 73%, more preferably at most 71%.
Al2O3 is an essential component to increase the chemical durability, particularly water resistance and/or acid resistance, and to suppress crystallization during firing. If it is less than 0.5%, its effect, i.e. the effect of increasing the chemical durability or the effect of suppressing crystallization during firing, tends to be too small. It is preferably at least 0.7%, more preferably at least 1%. If it exceeds 13%, the glass tends to be devitrified during melting. It is preferably at most 11%, more preferably at most 10%, particularly preferably at most 6%.
SnO2 is not essential, but has an effect of increasing the chemical durability, particularly water resistance, and may be contained up to 2%. If it exceeds 2%, no higher effect tends to be obtained any more, or the glass tends to be devitrified during melting. It is preferably at most 1.8%, more preferably at most 1.5%, particularly preferably at most 1%. In the case where SnO2 is contained, the content is preferably at least 0.2%. If it less than 0.2%, the above effect tends to be too small. It is more preferably at least 0.4%, particularly preferably at least 0.5%.
CeO2 is not essential, but may be contained up to 2% as an oxidizing agent. If it exceeds 2%, no higher effect tends to be obtained any more. It is preferably at most 1.8%, particularly preferably at most 1%.
Each of MgO, CaO and SrO is not essential, but may be contained up to 10% in total, in order to adjust the expansion coefficient. If it exceeds 10%, no higher effect tends to be obtained any more. It is preferably at most 9%.
ZnO is not essential, but may be contained up to 20% as a flux component. If it exceeds 20%, the glass tends to be devitrified during melting. It is preferably at most 18%.
Each of TiO2 and ZrO2 is not essential, but may be contained up to 5% each, in order to increase the chemical durability. If it exceeds 5%, the glass tends to be devitrified during melting. It is preferably at most 3% each, more preferably at most 2% each.
Each of Li2O, Na2O and K2O is not essential, but may be contained up to 5% each as a flux component. If it exceeds 5%, the expansion coefficient tends to be too high. It is preferably at most 4% each.
The glass of the present invention consists essentially of the above components, but may contain other components within a range of not impairing the object of the present invention. The total of contents of said other components is preferably at most 10%, more preferably at most 5%. Examples of said other components include a coloring component such as Fe2O3.
Here, NiO is a coloring component, but if it is contained in an amount exceeding 5%, the glass tends to be devitrified during melting, and thus the content is preferably at most 1%. It is more preferred that no NiO is contained substantially, i.e. its content is not higher than the impurity level.
Further, the glass of the present invention contains no lead, bismuth nor cadmium in an amount exceeding the impurity levels.
The glass ceramic composition of the present invention is fired to obtain a sintered product.
Now, the glass ceramic composition of the present invention will be described below, representing by mass%.
The powder of the glass of the present invention is an essential component. If it is less than 50%, the sintering degree, i.e. the denseness of the sintered product, will decrease. It is preferably at least 70%. The average particle size of the powder of the glass of the present invention is preferably from 0.5 to 10 xcexcm.
Either a ceramic filler or a heat resistant pigment is essential. If the total content of the ceramic filler and the heat resistant pigment is less than 0.1%, the effect by containing the ceramic filler and/or the heat resistant pigment is too small. If it exceeds 50%, the content of the powder of the glass of the present invention tends to be too small.
The ceramic filler is a component to adjust the expansion coefficient of the sintered product, and may be contained up to 50%. If it exceeds 50%, the sintering degree tends to decrease. It is preferably at most 30%.
The ceramic filler contains no lead, bismuth nor cadmium.
Examples of the ceramic filler include xcex1-alumina, xcex1-quartz, cordierite, stabilized zirconia, magnesia, forsterite, steatite, zircon and xcex2-eucryptite. The heat resistant pigment is a coloring component, and may be contained up to 30%. If it. exceeds 30%, the sintering degree tends to decrease. It is preferably at most 20%.
The heat resistant pigment contains no lead, bismuth -nor cadmium. Examples of the heat resistant pigment include a Cu-Cr-Mn-O type heat resistant black pigment, a Cu-Cr-O type heat resistant black pigment, a Co-V-Fe-O type heat resistant violet pigment, a Cr-O type heat resistant green pigment and a Co-O type heat resistant green pigment.
The glass ceramic composition of the present invention consists essentially of the above components, but may contain other components such as a powder of a glass other than the glass of the present invention, within a range of not impairing the object of the present invention. The total content of said other components is preferably at most 20%, more preferably at most 10%.
The sintered product of the glass ceramic composition of the present invention has a softening point by a differential thermal analysis of preferably from 600 to 800xc2x0 C.
The sintered product of the glass ceramic composition of the present invention has an expansion coefficient of preferably from 40xc3x9710xe2x88x927 to 100xc3x9710xe2x88x927
/xc2x0 C.
The glass ceramic composition of the present invention may be kneaded with a vehicle containing a resin component such as ethyl cellulose and a solvent such as xcex1-terpineol to obtain a paste, which is used for e.g. screen printing. Otherwise, it may be formed into a slurry, which is then formed into a green sheet, and a multi-layer construction may be prepared by using said green sheet. Here, the multi-layer construction may, for example, be prepared in such a manner that e.g. an electronic circuit pattern is formed on the green sheet by e.g. screen printing, and the resulting green sheets are laminated, followed by firing.
The glass ceramic composition of the present invention is suitable for e.g. insulating pastes for electronic parts, materials for sealing electronic parts, ceramic color pastes for automobile windows and glazes for dishes. Examples of the insulating pastes for electronic parts include overcoat pastes for hybrid IC (HIC), crossover pastes for HIC, multi-layer insulating glass pastes for HIC and overcoat pastes for print heads.